Patent GB-970897-A (GB)
Title: Improvements relating to grinding cement clinker and similar materials
Inventor: FRANKERT OTTO PREDER
IPC: B02C17/18
Filed: 1962-06-26
Abstract: 970,897. Tube mills ; reducing cements. F. L. SMIDTH & CO. A.S. June 26, 1963 [June 26, 1962], No. 24526/62. Heading B2A. [Also in Division G3]  Cement-clinker is ground in a mill having internal water injection for cooling purposes both between its inlet end and its centre and between its centre and its outlet end. As described, a compartmented, rotatable, mill-body 1 includes inlet and outlet trunnions 2, 3 and an inlet-hopper 6, ground material being carried away through a tube 10 and a gate-valve 12, and air being drawn through the mill via an electric dust-separator 13 to a chimney 15 by a pump 14. The mill is driven via membranecouplings 21, 22 and a reduction-gear 23 by a motor 24. Cooling water delivered from tanks 27, 28 is pumped by electric pumps 37, 38 along pipes 48, 49 through motor- or solenoidactuated valves 54, 55 to nozzles 50, 53 at opposite ends of the mill. A controlled flow of compressed air is applied to the nozzles along ducts 62, 63. In operation, when the motor 24 is started the rotary gate valve 12 12 operates, valves 61, 64, 65 controlling the compressed air supply are opened and the air clears the nozzles 50, 53 and grinding begins. When the temperature of ground material exceeds a set limit, e.g. 80 ‹C., a pyrometer 74 in the output feed-pipe 10 controls a cooling spray of water via the nozzle 53 into the final chamber III until the temperature falls. Similarly, if the temperature of material fed to the mill rises above a set limit, a pyrometer 72 in the inlet-hopper controls a cooling spray via nozzle 50 into the first chamber I. A rise in temperature above a further limit, e.g. 100 ‹C., causes full opening of the valve 54 and a large spray of cooling water, and, if the temperature continues to rise, the mill and its feed device are automatically stopped. Each dividing diaphragm 16, 17 is formed by a thin slotted steel plate 81, Fig. 2, and a thicker plate 84 having a central opening 85 corresponding with an opening 83 in the plate 81. Air is sucked through the openings and ground material passes through the slots and is lifted by curved scoops 86 which also act as separators between the plates. A pyrometer 88, which may replace or supplement the pyrometers 72, 74, may be mounted within the space between the walls of the diaphragm with lead wires 89, 90 connected to contact rings 91, 92. A terminal is resiliently pressed against each of the rings 91, 92 which are kept in position in relation to the shell of the mill by supports 93, 94 bolted thereto. In a further embodiment, cement clinker and gypsum in silos 108, 109, Fig. 4, are weighed in feeders 110, 111, and the mill includes a double diaphragm 102, and a single diaphragm 103 having a central aperture, and is supported in neck-journal bearings 106, 107 at each end. The water injection for the first stage includes two nozzles 117, 118, water from the nozzle 117 striking the region near the diaphragm 102, and water from the nozzle 118 striking the mill near the feed entry. A pyrometer 131 in the cement clinker silo 108 controls the primary spray nozzle 118 by a valve 123, and a pyrometer 132 in the interior wall of the casing 113 controls a valve 122 for the secondary  spray 117. The nozzles may be arranged to prevent interference with the jets, by having a central secondary-nozzle-bearing cylinder fed by one pipe, and an outer ring of primary nozzles surrounding it and fed by a second pipe. Another embodiment includes primary and secondary sprays at the inlet and outlet ends of the chamber I. The pyrometer for controlling the secondary spray is sited within the double diaphragm, arid the feed from the control valve to the nozzle enters the mill via a stuffing box, which also permits entry of a regulator supply to feed the nozzle in the third compartment of the mill. Mills may be provided with four or more compartments, and spraying may be applied in different combinations of compartments. A double diaphragm may be provided with nozzles to effect spraying into the two compartments separated by the diaphragm.